Bioactive hydrogels based on polysaccharides and peptides for soft tissue wound management

Progress in injectable hydrogels for hard tissue regeneration in the last decade

Bone disorders have increased with increasing the human lifespan, and despite the tissue's ability to self-regeneration, in many congenital problems and hard fractures, bone grafting such as autograft, allograft, and biomaterials implantation through surgery is traditionally used. Because of the adverse effects of these methods, the emergence of injectable hydrogels without the need for surgery and causing more pain for the patient is stunning to develop a new pattern for hard tissue engineering. These materials are formed with various natural and synthetic polymers with a crosslinked network through various chemical methods such as click chemistry, Michael enhancement, Schiff's base and enzymatic reaction and physical interactions with high water absorption which can mimic the environment of cells. The purpose of this research is to review the capabilities of this class of materials in hard tissue regeneration in the last decade through adaptable physical and chemical properties, the ability to fill defect sites with an irregular shape, and the ability to grow hormones or release drugs, in response to external stimuli.

Design Strategy, On-Demand Control, and Biomedical Engineering Applications of Wet Adhesion

The adhesion of tissues to external devices is fundamental to numerous critical applications in biomedical engineering, including tissue and organ repair, bioelectronic interfaces, adhesive robotics, wearable electronics, biomedical sensing and actuation, as well as medical monitoring, treatment, and healthcare. A key challenge in this context is that tissues are typically situated in aqueous and dynamic environments, which poses a bottleneck to further advancements in these fields. Wet adhesion technology (WAT) presents an effective solution to this issue. In this review, we summarize the three major design strategies and control methods of wet adhesion, comprehensively and systematically introducing the latest applications and advancements of WAT in the field of biomedical engineering. First, single adhesion mechanism under the frameworks of the three design strategies is systematically introduced. Second, control methods for adhesion are comprehensively summarized, including spatiotemporal control, detachment control, and reversible adhesion control. Third, a systematic summary and discussion of the latest applications of WAT in biomedical engineering research and education were presented, with a particular focus on innovative applications such as tissue-electronic interface devices, ingestible devices, end-effector components, in vivo medical microrobots, and medical instruments and equipment. Finally, opportunities and challenges encountered in the design and development of wet adhesives with advanced adhesive performance and application prospects are discussed.

Triple-crosslinked double-network alginate/dextran/dendrimer hydrogel with tunable mechanical and adhesive properties: A potential candidate for sutureless keratoplasty

An ideal adhesive hydrogel must possess high adhesion to the native tissue, biocompatibility, eligible biodegradability, and good mechanical compliance with the substrate tissues. We constructed an interpenetrating double-network hydrogel containing polysaccharides (alginate and dextran) and nanosized spherical dendrimer by both physical and chemical crosslinking, thus endowing the hydrogel with a broad range of mechanical properties, adhesive properties, and biological functions. The double-network hydrogel has moderate pore sizes and swelling properties. The chelation of calcium ions significantly enhances the tensile and compressive properties. The incorporation of dendrimer improves both the mechanical and adhesive properties. This multicomponent interpenetrating network hydrogel has excellent biocompatibility, tunable mechanical and adhesive properties, and satisfied multi-functions to meet the complex requirements of wound healing and tissue engineering. The hydrogel exhibits promising corneal adhesion capabilities in vitro, potentially supplanting the need for sutures in corneal stromal surgery and mitigating the risks associated with donor corneal damage and graft rejection during corneal transplantation. This novel polysaccharide and dendrimer hydrogel also shows good results in sutureless keratoplasty, with high efficiency and reliability. Based on the clinical requirements for tissue bonding and wound closure, the hydrogel provides insight into solving the mechanical properties and adhesive strength of tissue adhesives.

Metal-organic frameworks: synthesis, properties, wound dressing, challenges and scopes in advanced wound dressing

Wound healing is a critical but complex biological process of skin tissue repair and regeneration resulting from various systems working together at the cellular and molecular levels. Quick wound healing and the problems associated with traditional wound repair techniques are being overcome with multifunctional materials. Over time, this research area has drawn significant attention. Metal-organic frameworks (MOFs), owning to their peculiar physicochemical characteristics, are now considered a promising class of well-suited porous materials for wound healing in addition to their other biological applications. This detailed literature review provides an overview of the latest developments in MOFs for wound healing applications. We have discussed the synthesis, essential biomedical properties, wound-healing mechanism, MOF-based dressing materials, and their wound-healing applications. The possible major challenges and limitations of MOFs have been discussed, along with conclusions and future perspectives. This overview of the literature review addresses MOFs-based wound healing from several angles and covers the most current developments in the subject. The readers may discover how the MOFs advanced this discipline by producing more inventive, useful, and successful dressings. It influences the development of future generations of biomaterials for the healing and regeneration of skin wounds.

Hydrogel-Based Novel Biomaterials: Achievements and Prospects

In recent decades, hydrogels have garnered significant attention, thanks to their extensive biomedical and pharmaceutical applications [...].

Modular co-assembly of peptides and polyoxometalates into underwater adhesives with photoluminescence and adjustable adhesion

Supramolecular polymerization between cationic peptides and anionic polyoxometalates has emerged as a promising strategy for the creation of peptide-based biomimetic underwater adhesives. However, the extremely rigorous requirements for peptide design are an important obstacle to the fabrication of available peptide adhesives with controlled adhesion and versatile functionality. Inspired by marine sessile organisms in nature, here we reported a modular co-assembly method to easily produce peptide/polyoxometalate underwater adhesive materials through mixing two complementary cationic peptides (Pep1 and Pep2) with a single anionic polyoxometalate K6H[SiW9V3O40] in aqueous solution, which are not possible to be obtained from an individual peptide module. We demonstrated that the relatively hydrophobic Pep1 contributes to the bulk cohesion of the resulting adhesive, while the relatively hydrophilic Pep2 not only enables the interfacial adhesion but also regulates the bulk cohesion of the Pep1/Pep2/SiW9V3 adhesive. Rheological and shear adhesion tests showed that the macroscopic adhesion performance of the resulting adhesive materials could be conveniently adjusted by simply changing the molar ratio of the complementary peptide modules without any complicated peptide design. Interestingly, the luminescence properties of K11[Eu(PW11O39)2] (labelled as EuPW11) could be maintained within the Pep1/Pep2/EuPW11 adhesive even in a water environment. The lifetime of the Pep1/Pep2/EuPW11 adhesive was 2.19 ms. The fluorescence quantum yield of the Pep1/Pep2/EuPW11 adhesive was measured to be 27.46%. This study unveils that the modular co-assembly method can effectively simplify the material design of peptide/polyoxometalate underwater adhesives, which will significantly broaden the horizon of material pools and extend their availability space.

Optimization and Characterization of a Novel Antioxidant Naringenin-Loaded Hydrogel for Encouraging Re-Epithelization in Chronic Diabetic Wounds: A Preclinical Study

Nonhealed wounds are one of the most dangerous side effects of type-2 diabetes, which is linked to a high frequency of bacterial infections around the globe that eventually results in amputation of limbs. The present investigation aimed to explore the drug-loaded (naringenin) hydrogel system for chronic wound healing. The hydrogel membranes comprising Na-alginate with F-127 and poly(vinyl alcohol) were developed to treat chronic wounds using the quality-by-design (QbD) approach. The optimized formulation was tested for various parameters, such as swelling, gel fraction, water vapor transition rate (WVTR), etc. In vitro evaluation indicated that a drug-loaded hydrogel displayed better tissue adhesiveness and can release drugs for a prolonged duration of 12 h. Scratch assay performed on L929 cell lines demonstrated good cell migration. The diabetic wound healing potential of the hydrogel membrane was assessed in streptozotocin-induced male Wistar rats (50 mg/kg). Higher rates of wound closure, re-epithelialization, and accumulation of collagen were seen in in vivo experiments. Histopathologic investigation correspondingly implied that the drug-loaded hydrogel could enhance dermal wound repair. The improved antimicrobial and antioxidant properties with expedited healing indicated that the drug-loaded hydrogel is a perfect dressing for chronic wounds.

Exopolysaccharides Producing Bacteria: A Review

Bacterial exopolysaccharides (EPS) are essential natural biopolymers used in different areas including biomedicine, food, cosmetic, petroleum, and pharmaceuticals and also in environmental remediation. The interest in them is primarily due to their unique structure and properties such as biocompatibility, biodegradability, higher purity, hydrophilic nature, anti-inflammatory, antioxidant, anti-cancer, antibacterial, and immune-modulating and prebiotic activities. The present review summarizes the current research progress on bacterial EPSs including their properties, biological functions, and promising applications in the various fields of science, industry, medicine, and technology, as well as characteristics and the isolation sources of EPSs-producing bacterial strains. This review provides an overview of the latest advances in the study of such important industrial exopolysaccharides as xanthan, bacterial cellulose, and levan. Finally, current study limitations and future directions are discussed.

Hydrogel scaffolds in the treatment of spinal cord injury: a review

Spinal cord injury (SCI) is a disease of the central nervous system often caused by accidents, and its prognosis is unsatisfactory, with long-term adverse effects on patients' lives. The key to its treatment lies in the improvement of the microenvironment at the injury and the reconstruction of axons, and tissue repair is a promising therapeutic strategy. Hydrogel is a three-dimensional mesh structure with high water content, which has the advantages of biocompatibility, degradability, and adjustability, and can be used to fill pathological defects by injectable flowing hydrophilic material in situ to accurately adapt to the size and shape of the injury. Hydrogels mimic the natural extracellular matrix for cell colonization, guide axon extension, and act as a biological scaffold, which can be used as an excellent carrier to participate in the treatment of SCI. The addition of different materials to make composite hydrogel scaffolds can further enhance their performance in all aspects. In this paper, we introduce several typical composite hydrogels and review the research progress of hydrogel for SCI to provide a reference for the clinical application of hydrogel therapy for SCI.

Rosmarinic Acid-Grafted Dextran/Gelatin Hydrogel as a Wound Dressing with Improved Properties: Strong Tissue Adhesion, Antibacterial, Antioxidant and Anti-Inflammatory

Designing a strong tissue adhesive and multifunctional hydrogel dressing for various skin injuries is still a significant challenge. Based on the bioactive activities of rosmarinic acid (RA) and its catechol structure being similar to dopamine, RA-grafted dextran/gelatin hydrogel (ODex-AG-RA) was designed and systemically characterized in this study. The ODex-AG-RA hydrogel exhibited excellent physicochemical properties, including fast gelation time (61.6 ± 2.8 s), strong adhesive strength (27.30 ± 2.02 kPa) and enhanced mechanical properties (1.31 × 10⁴ Pa of G'). The examination of hemolysis and co-culturing with L929 cells showed the strong in vitro biocompatibility of ODex-AG-RA hydrogels. The ODex-AG-RA hydrogels exhibited a 100% mortality rate against S. aureus and at least 89.7% against E. coli in vitro. In vivo evaluation for efficacy in skin wound healing was carried out in a rat model of full-thickness skindefect. The amount of collagen deposition and CD31 on wounds in the two ODex-AG-RA-1 groups on day 14 was 4.3 times and 2.3 times of that in the control group, respectively. Furthermore, the mechanism of ODex-AG-RA-1 for promoting wound healing was proved to be related to its anti-inflammatory properties by adjusting the expression of inflammatory cytokines (TNF-α and CD163) and reducing the level of oxidative stress (MDA and H₂O₂). Overall, this study demonstrated the wound-healing efficacy of RA-grafted hydrogels for the first time. ODex-AG-RA-1 hydrogel, due to its adhesive, anti-inflammatory, antibacterial and antioxidative activities, was a promising candidate as a wound dressing.

Research progress of hydrogels as delivery systems and scaffolds in the treatment of secondary spinal cord injury

Secondary spinal cord injury (SSCI) is the second stage of spinal cord injury (SCI) and involves vasculature derangement, immune response, inflammatory response, and glial scar formation. Bioactive additives, such as drugs and cells, have been widely used to inhibit the progression of secondary spinal cord injury. However, the delivery and long-term retention of these additives remain a problem to be solved. In recent years, hydrogels have attracted much attention as a popular delivery system for loading cells and drugs for secondary spinal cord injury therapy. After implantation into the site of spinal cord injury, hydrogels can deliver bioactive additives in situ and induce the unidirectional growth of nerve cells as scaffolds. In addition, physical and chemical methods can endow hydrogels with new functions. In this review, we summarize the current state of various hydrogel delivery systems for secondary spinal cord injury treatment. Moreover, functional modifications of these hydrogels for better therapeutic effects are also discussed to provide a comprehensive insight into the application of hydrogels in the treatment of secondary spinal cord injury.

Injectable and Self-Healing Hydrogel Based on Chitosan-Tannic Acid and Oxidized Hyaluronic Acid for Wound Healing

Self-healing performance plays an important role in the in situ microinvasive injection of hydrogels, which can reduce sudden drug release and prolong the service life of hydrogels. In this paper, a multifunctional injectable and self-healing hydrogel for wound healing was developed. Chitosan (CS) was modified with TA to achieve potential adhesion, anti-inflammatory properties, and slower degradation rate. The hydrogel was formed by Schiff base reaction based on amino groups in CS and aldehyde groups in oxidized hyaluronic acid (OHA). The gel formation process was quick and convenient in mild conditions without extra initiators. Due to the dynamically reversible covalent bonds, the hydrogel could self-heal within 2 min after injection. It also had good biocompatibility and hemostatic performance. With the addition of TA, the hydrogel acquired anti-inflammatory properties and promoted cell growth, effectively accelerating the wound-healing process in vivo. The CS-TA/OHA hydrogel is expected to be used for skin repair.

Research Progress on Emerging Polysaccharide Materials Applied in Tissue Engineering

The development and application of polysaccharide materials are popular areas of research. Emerging polysaccharide materials have been widely used in tissue engineering fields such as in skin trauma, bone defects, cartilage repair and arthritis due to their stability, good biocompatibility and reproducibility. This paper reviewed the recent progress of the application of polysaccharide materials in tissue engineering. Firstly, we introduced polysaccharide materials and their derivatives and summarized the physicochemical properties of polysaccharide materials and their application in tissue engineering after modification. Secondly, we introduced the processing methods of polysaccharide materials, including the processing of polysaccharides into amorphous hydrogels, microspheres and membranes. Then, we summarized the application of polysaccharide materials in tissue engineering. Finally, some views on the research and application of polysaccharide materials are presented. The purpose of this review was to summarize the current research progress on polysaccharide materials with special attention paid to the application of polysaccharide materials in tissue engineering.